The present invention relates to a thermalconductive sheet that is used as a member of a heat dissipation and cooling structure for heat generating electronic parts and the like, especially to a thermalconductive sheet with low rigidity that is used for dissipating heat and cooling of heat generating electronic parts and the like.
In the past, the following types of thermalconductive sheets with low rigidity have been proposed as a member of a heat dissipation and cooling structure for heat generating electronic parts and the like:
(1) A thermalconductive sheet that is not deformed or damaged by the compression of a heat generating electronic member (referred to below as xe2x80x9cchipxe2x80x9d) and a heat sink, because the compression load on the sheet is held low when the sheet is compressed to establish a tight contact (referred to below as xe2x80x9ccontact compressionxe2x80x9d) between the chip and the heat sink.
(2) A thermalconductive sheet that is tightly contacted when being contact-compressed between a chip and a heat sink having an uneven surface on the contact side, because the thermalconductive sheet is elastic, thus ensuring a sufficiently large thermalconductive surface.
(3) A thermalconductive sheet that (a) has sufficiently tight contact with all of a plurality of chips mounted on a board, and (b) that is not deformed or damaged by the compression of the chips and a heat sink when being contact-compressed between the plurality of chips and the heat sink, because the thermalconductive sheet is elastic.
A silicone gel sheet containing a thermalconductive filler, and Japanese Tokkai No. Hei 2-166755, No. Hei 2-196453, and No. Hei 2-155517 are known as examples for such thermalconductive sheets.
However, a silicone gel sheet containing a thermalconductive filler, and a thermalconductive silicone gel sheet having grooves on one or both sides (Tokkai Hei 2-166755), are extremely soft and lack strength, and therefore pose severe problems regarding the handling of the sheets during the mounting process. Furthermore, because both sides of the sheet have roughly the same degree of stickiness, the sheet may stick to both the chip and the heat sink when releasing the contact compression between the chip and the heat sink for maintenance after the mounting, resulting in extreme deformation or even rupture, and thus making reuse of the sheet impossible.
A compound thermalconductive sheet, wherein a silicone gel containing a thermalconductive filler is layered and hardened on a silicone rubber sheet containing a thermalconductive filler (Tokkai Hei 2-196453), and a thermalconductive compound sheet, wherein a low rigidity silicone rubber containing a thermalconductive filler is integrated with a sheet made by coating a meshed reinforcement material with a silicone rubber containing a thermalconductive filler and then hardened (Tokkai Hei 2-196453), are both soft in a direction perpendicular to the sheet, rigid in the in-plane direction and sticky only on one side and therefore easy to handle during the mounting process and can be reused after release of the contact compression. However, because the compressibility of such sheets is about 2 to 5 times higher than the compressibility of a single thermalconductive silicone gel sheet, these sheets cannot be used when the mounting electronic parts such as chips, heat sinks, and boards having low rigidity, or when the height difference of a plurality of chips mounted on a board is large.
It is the purpose of the present invention to overcome the problems of the prior art by providing a formed sheet of thermalconductive silicone gel that has a low compressibility and a high rigidity, that is easy to handle during the mounting process, and that can be reused after the release of the contact compression with a chip and a heat sink.
A first formed sheet of thermalconductive silicone gel according to the present invention is characterized in that a thin film reinforcement layer is hardened into rubber in a surface layer on at least one side of the sheet.
In the first formed sheet of thermalconductive silicone gel according to the present invention it is preferable that a silicone gel containing a thermalconductive filler is sandwiched between (a) a resin film to which has been applied an organohydrogen polysiloxane containing at least two hydrogen atoms bonded to a silicon atom in each molecule and (b) a resin film to which said organohydrogen polysiloxane has not been applied, or sandwiched between two resin films to which said organohydrogen polysiloxane has been applied; rolled by being continually passed through at least one pair of rolls; continually passed through a heating furnace; and hardened; in order to form a thin film reinforcement layer hardened into rubber on at least one side of the sheet.
A second formed sheet of thermalconductive silicone gel according to the present invention is characterized in that a thin film reinforcement layer is hardened into rubber in a surface layer on at least one side of the sheet, and a sheet-shaped reinforcement material is buried in a surface layer on one side of the sheet.
In the second formed sheet of thermalconductive silicone gel according to the present invention, it is preferable that a silicone gel containing a thermalconductive filler is sandwiched between (a) a resin film having a surface to which has been applied an organohydrogen polysiloxane containing at least two hydrogen atoms bonded to a silicon atom in each molecule, and onto which surface a sheet-shaped reinforcement layer has been layered and (b) a resin film to which said organohydrogen polysiloxane has not been applied, or between two resin films to which said organohydrogen polysiloxane has been applied; rolled by being continually passed through at least one pair of rolls; continually passed through a heating furnace; and hardened; in order to form a sheet-shaped reinforcement material buried in a surface layer on one side of the sheet and a thin film reinforcement layer hardened into rubber on at least one side of the sheet.
In the first and second formed sheet of thermalconductive silicone gel according to the present invention, it is preferable that the hardness of the thin film reinforcement layer is in the range of 10-95 when measured with an ASKER F hardness meter. It is even more preferable that the hardness of the thin film reinforcement layer is in the range of 20-70 when measured with an ASKER F hardness meter.
In the first and second formed sheet of thermalconductive silicone gel according to the present invention, it is preferable that the thickness of the thin film reinforcement layer is in the range of 0.01-0.5 mm. It is even more preferable that the thickness of the thin film reinforcement layer is in the range of 0.01-0.1 mm.
A third formed sheet of thermalconductive silicone gel according to the present invention is characterized in that a sheet-shaped reinforcement material is buried in a surface layer on one side of a formed sheet of silicon gel containing a thermalconductive filler.
In the third formed sheet of thermalconductive silicone gel according to the present invention, it is preferable that a silicone gel containing a thermalconductive filler is sandwiched between (a) a resin film onto whose surface a sheet-shaped reinforcement layer has been layered and (b) a resin film onto whose surface a sheet-shaped reinforcement layer has not been layered; rolled by being continually passed through at least one pair of rolls; continually passed through a heating furnace; and hardened; in order to form to form a sheet-shaped reinforcement material buried in a surface layer on one side of the sheet.
In the second and third formed sheet of thermalconductive silicone gel according to the present invention, it is preferable that the depth to which the sheet-shaped reinforcement material is buried in a surface layer on one side of the sheet is in the range of more than 0 mm but not more than 1 mm. Here, the term xe2x80x9cdepthxe2x80x9d indicates the distance from the upper surface of the reinforcement material to the upper surface of the gel. It is even more preferable that the depth to which the sheet-shaped reinforcement material is buried in a surface layer on one side of the sheet is in the range of more than 0 mm but not more than 0.5 mm.
In the second and third formed sheet of thermalconductive silicone gel according to the present invention, it is preferable that the sheet-shaped reinforcement material buried in a surface layer on one side of the sheet has a mesh fabric structure using at least one fiber selected from synthetic fiber and natural fiber.
A first method of manufacturing a formed sheet of thermalconductive silicone gel according to the present invention comprises the steps of: sandwiching a silicone gel containing a thermalconductive filler between (a) a resin film to which has been applied an organohydrogen polysiloxane containing at least two hydrogen atoms bonded to a silicon atom in each molecule and (b) a resin film to which said organohydrogen polysiloxane has not been applied, or sandwiching said silicone gel between two resin films to which said organohydrogen polysiloxane has been applied; rolling the silicone gel by continually passing the silicone gel through at least one pair of rolls; and hardening the silicone gel by continually passing the silicone gel through a heating furnace.
A second method of manufacturing a formed sheet of thermalconductive silicone gel according to the present invention comprises the steps of: sandwiching a silicone gel containing a thermalconductive filler between (a) a resin film having a surface to which has been applied an organohydrogen polysiloxane containing at least two hydrogen atoms bonded to a silicon atom in each molecule, and onto which surface a sheet-shaped reinforcement layer has been layered and (b) a resin film to which said organohydrogen polysiloxane has not been applied, or sandwiching the silicone gel between two resin films to which said organohydrogen polysiloxane has been applied; rolling the silicone gel by being continually passing it through at least one pair of rolls; and hardening the silicone gel by continually passing the silicone gel through a heating furnace.
A third method of manufacturing a formed sheet of thermalconductive silicone gel according to the present invention comprises the steps of: sandwiching a silicone gel containing a thermalconductive filler between (a) a resin film onto whose surface a sheet-shaped reinforcement layer has been layered and (b) a resin film onto whose surface a sheet-shaped reinforcement layer has not been layered; rolling the silicone gel by being continually passed through at least one pair of rolls; and hardening the silicone gel by continually passing the silicone gel through a heating furnace.